An automatic command is installed that runs luac -p when you save your Lua scripts. If luac reports any errors they are shown in the quick-fix list and Vim jumps to the line of the first error. If luac -p doesn't report any errors a check for undefined global variables is performed by parsing the output of luac -p -l

K (normal mode) and <F1> (insert mode) on a Lua function or 'method' call will try to open the relevant documentation in the Lua Reference for Vim

The 'completefunc' option is set to allow completion of Lua 5.2 keywords, global variables and library members using Control-X Control-U

The 'omnifunc' option is set to allow dynamic completion of the variables defined in all modules installed on the system using Control-X Control-O, however it needs to be explicitly enabled by setting the lua_complete_omni option because this functionality may have undesired side effects! When you invoke omni completion after typing require ' or require(' you get completion of module names

Several text-objects are defined so you can jump between blocks and functions

A pretty nifty hack of the matchit plug-in is included: When the cursor is on a function or return keyword the % mapping cycles between the relevant keywords (function, return, end), this also works for branching statements (if, elseif, else, end) and looping statements (for, while, repeat, until, end)

Now try it out: Edit a Lua script and try any of the features documented above.

Note that on Windows a command prompt window pops up whenever Lua is run as an external process. If this bothers you then you can install my shell.vim plug-in which includes a DLL that works around this issue. Once you've installed both plug-ins it should work out of the box!

Options

The Lua file type plug-in handles options as follows: First it looks at buffer local variables, then it looks at global variables and if neither exists a default is chosen. This means you can change how the plug-in works for individual buffers. For example to change the location of the Lua compiler used to check the syntax:

" This sets the default value for all buffers.
:let g:lua_compiler_name = '/usr/local/bin/luac'
" This is how you change the value for one buffer.
:let b:lua_compiler_name = '/usr/local/bin/lualint'

The lua_path option

This option contains the value of package.path as a string. You shouldn't need to change this because the plug-in is aware of $LUA_PATH and if that isn't set the plug-in will run a Lua interpreter to get the value of package.path.

The lua_check_syntax option

When you write a Lua script to disk the plug-in automatically runs the Lua compiler to check for syntax errors. To disable this behavior you can set this option to false (0):

let g:lua_check_syntax = 0

You can manually check the syntax using the :CheckSyntax command.

The lua_check_globals option

When you write a Lua script to disk the plug-in automatically runs the Lua compiler to check for undefined global variables. To disable this behavior you can set this option to false (0):

let g:lua_check_globals = 0

You can manually check the globals using the :CheckGlobals command.

The lua_interpreter_path option

The name or path of the Lua interpreter used to evaluate Lua scripts used by the plug-in (for example the script that checks for undefined global variables, see :LuaCheckGlobals).

The lua_internal option

If you're running a version of Vim that supports the Lua Interface for Vim (see if_lua.txt) then all Lua code evaluated by the Lua file type plug-in is evaluated using the Lua Interface for Vim. If the Lua Interface for Vim is not available the plug-in falls back to using an external Lua interpreter. You can set this to false (0) to force the plug-in to use an external Lua interpreter.

The lua_compiler_name option

The name or path of the Lua compiler used to check for syntax errors (defaults to luac). You can set this option to run the Lua compiler from a non-standard location or to run a dedicated syntax checker like lualint.

The lua_compiler_args option

The argument(s) required by the compiler or syntax checker (defaults to -p).

The lua_error_format option

If you use a dedicated syntax checker you may need to change this option to reflect the format of the messages printed by the syntax checker.

The lua_complete_keywords option

To disable completion of keywords you can set this option to false (0).

The lua_complete_globals option

To disable completion of global functions you can set this option to false (0).

The lua_complete_library option

To disable completion of library functions you can set this option to false (0).

The lua_complete_dynamic option

When you type a dot after a word the Lua file type plug-in will automatically start completion. To disable this behavior you can set this option to false (0).

The lua_complete_omni option

This option is disabled by default for two reasons:

The omni completion support works by enumerating and loading all installed modules. If module loading has side effects this can have unintended consequences!

Because all modules installed on the system are loaded, collecting the completion candidates can be slow. After the first run the completion candidates are cached so this will only bother you once (until you restart Vim).

If you want to use the omni completion despite the warnings above, execute the following command:

:let g:lua_complete_omni = 1

Now when you type Control-X Control-O Vim will hang for a moment, after which you should be presented with an enormous list of completion candidates :-)

The lua_omni_blacklist option

If you like the omni completion mode but certain modules are giving you trouble (for example crashing Vim) you can exclude such modules from being loaded by the omni completion. You can do so by setting lua_omni_blacklist to a list of strings containing Vim regular expression patterns. The patterns are combined as follows:

The example above prevents the module pl.strict and all modules with the prefix lgi. from being loaded.

The lua_safe_omni_modules option

To track down modules that cause side effects while loading, setting

:let g:lua_safe_omni_modules = 1

restricts the modules to be loaded to the standard Lua modules - which should be safe to load - and provides a list of modules that would have been loaded if this option was not set via the :messages command. With this list, the lua_omni_blacklist can be iteratively refined to exclude offending modules from omni completion module loading.

Note that the 'verbose' option has to be set to 1 or higher for the list to be recorded.

The lua_define_completefunc option

By default the Lua file type plug-in sets the 'completefunc' option so that Vim can complete Lua keywords, global variables and library members using Control-X Control-U. If you don't want the 'completefunc' option to be changed by the plug-in, you can set this option to zero (false) in your vimrc script:

:let g:lua_define_completefunc = 0

The lua_define_omnifunc option

By default the Lua file type plug-in sets the 'omnifunc' option so that Vim can complete the names of all Lua modules installed on the local system. If you don't want the 'omnifunc' option to be changed by the plug-in, you can set this option to zero (false) in your vimrc script:

:let g:lua_define_omnifunc = 0

The lua_define_completion_mappings option

By default the Lua file type plug-in defines insert mode mappings so that the plug-in is called whenever you type a single quote, double quote or a dot inside a Lua buffer. This enables context sensitive completion. If you don't like these mappings you can set this option to zero (false). In that case the mappings will not be defined.

Commands

The :LuaCheckSyntax command

Check the current file for syntax errors using the Lua compiler. This command is executed automatically when you write a Lua script to disk (i.e. when you save your changes) unless lua_check_syntax is false.

The :LuaCheckGlobals command

Check the current file for undefined global variables. This command is executed automatically when you write a Lua script to disk (i.e. when you save your changes) unless lua_check_globals is false or syntax errors were detected.